1. Field of the Invention
The present invention relates to a printer in which a platen roller and a recording head are separably combined with each other.
2. Description of the Related Art
As conventionally known printers, there are given printers in which a recording head and a platen roller held in contact with the recording head are provided inside a casing, and in which the recording head performs recording onto a recording sheet sent out by the platen roller. In the printers of this type, for example, at the time of setting of the recording sheet or jam treatment, or at the time of maintenance or replacement of the recording head, the platen roller, and the like, the recording head and the platen roller remain in contact with each other inside the casing. Thus, workability is poor.
In view of this, it is desired that the recording head and the platen roller be spaced apart from each other so as to be exposed to an outside of the casing. In particular, the recording head includes a plurality of recording elements (heat-generating elements or the like), and hence it is preferred that the recording head be fixed on a casing side in order not to impair reliability of electrical connections into which recording signals for selectively driving the recording elements are input. In other words, it is desired that the platen roller be spaced apart from the recording head so as to be exposed to the outside, with the recording head being fixed on the casing side.
For satisfaction current demands, there have been provided some printers in which the platen roller is freely attachable and detachable and, at the time of attachment, the platen roller is retained under a state of being held in contact with the recording head at a predetermined pressure.
As one of the printers, there has been known a printer which includes a regulating member and a stationary frame, in which a platen roller can be easily attached and detached with use of those members, and in which the platen roller can be retained with high reliability while the platen roller is prevented from being inadvertently disengaged at the time of mounting (refer to JP 4376816B).
The regulating member includes a connecting portion into which a shaft portion of the platen roller is fitted, and the regulating member is undisengageably combined with the platen roller through intermediation of the connecting portion. Meanwhile, the regulating member is rotatably combined coaxially with and relatively to the platen roller. Note that, regarding movement except the relative rotation, the regulating member moves integrally with the platen roller. Further, the regulating member is provided with a protrusion-like engagement portion.
Meanwhile, the stationary frame is fixed to abase of a casing, and includes a first recess and a second recess. The first recess is a recess for positioning the platen roller to a recordable position by bringing the platen roller into contact with the recording head when the shaft portion of the platen roller is inserted. The second recess is a recess for retaining a protrusion of the stationary frame when the protrusion is inserted under a state in which the shaft portion of the platen roller is inserted in the first recess.
When the platen roller is attached in the printer structured as described above, the shaft portion of the platen roller is inserted in the first recess and retained therein, and then the regulating member is rotated relatively to the platen roller and the protrusion is inserted into the second recess and retained therein. With this, at the recordable position at which the platen roller is held in contact with the recording head, the platen roller can be reliably retained.
In particular, due to a positional relation, shapes, and the like of the first recess and the second recess, even with application of an external force, for example, the platen roller is prevented from being disengaged from the first recess, and the platen roller and the protrusion are prevented from being disengaged respectively from the first recess and the second recess. In other words, the printer is designed so that the platen roller is less liable to be inadvertently disengaged. Thus, the platen roller can be retained with high reliability.
Meanwhile, when the platen roller is detached, the regulating member is rotated relatively to the platen roller (rotated in a direction reverse to that in the above-mentioned case). Consequently, the protrusion is disengaged from the second recess, and then the shaft portion of the platen roller is disengaged from the first recess. In this manner, the platen roller can be detached.
As described above, the platen roller can be attached and detached with a simple manipulation of rotating the regulating member so that the protrusion is inserted into or disengaged from the second recess. Thus, the printer is excellent in manipulation properties of attachment and detachment.
By the way, as well as for various electronic apparatuses, further downsizing of printers will be required also in the future. Thus, it is desired that the printers be structured as simply as possible and components be designed to be small. In particular, the platen roller for feeding the recording sheet is larger among the components of the printers, and hence occupies a large space in the printer. Thus, downsizing of the printer is efficiently achieved through possible reduction of a diameter of the platen roller.
In this regard, in the above-mentioned conventional printer, it is structurally difficult to reduce the diameter of the platen roller, and hence there has been a room for improvement . Specifically, the connecting portion of the regulating member is coaxially fitted into the shaft portion of the platen roller. Accordingly, when the diameter of the platen roller is reduced, it is necessary to reduce an outer diameter of the connecting portion in accordance therewith. However, in order to reliably fit the connecting portion into the shaft portion without backlash or the like, it is structurally necessary to secure a certain outer diameter. Accordingly, it is practically difficult to further reduce the diameter of the platen roller at present.